Answer: Bulb layering is a great idea -- but it can be difficult to do well.
It basically means planting a variety of bulbs in layers one above the other at different depths into the soil. Usually it is done with a mix of early spring bulbs such as tulips planted together with crocus. This would provide an early bloom of little crocus followed by a later bloom of the larger tulips. The crocus are planted about three inches down and the tulips are planted about 5 inches down so there is room for everything in the soil. The crocus fooliage remains and ripens while the tulips come up and bloom.
The benefit to this is that you can arrange two displays using only one space. The downside is that when you need to dig and divide or replace the tulips, you must also move all of the crocus out of the way. The thick bulb planting makes it difficult to plant annuals over the bulbs, so that means you will have a blank space there for the rest of the season.
In my experience, this method works best as naturalized plantings which are not in a "showplace" area of the garden the rest of the season, or as seasonal container displays which you simply plan on replacing every year.
I am not sure you could fit enough varieties of summer blooming bulbs into a layered planting to achieve bloom for the entire season. (Most perennial summer bulbs such as lilies are large plants and could not be layered with annuals such as gladiolus as they would crowd each other out.)
You might consider instead planting bulbs in containers which you then lift and replace as the bulbs cycle through the bloom period. I particularly suggest this because bulbs need to grow and ripen their foliage after blooming and can look very ugly in this stage. If not allowed to grow and ripen their foliage, they will not bloom the following year. Furthermore, many of the summer bulbs are not winter hardy and need to be lifted and stored indoors over the winter. Growing them in containers simplifies that process, too.
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